83 entries under persistent topic. ×

20
inexorable(adjective, characteristic, mean, strong, hard)
19
unyielding(adjective, characteristic, mean, strong, hard)
16
firm(noun, adjective, mean, strong, hard)
16
rigid(adjective, mean, strong, hard, tough)
15
adamant(adjective, mean, strong, hard, strength)
15
stubborn(adjective, characteristic, quality, mean, strong)
14
obdurate(adjective, strong, hard, tough, firm)
13
inflexible(adjective, mean, strong, hard, tough)
13
relentless(adjective, mean, strong, hard, tough)
13
unrelenting(adjective, mean, hard, tough, resist)
12
unbending(adjective, mean, strong, hard, tough)
11
implacable(adjective, mean, strong, hard, tough)
11
uncompromising(adjective, mean, hard, resist, determined)
10
adamantine(adjective, set, strong, hard, tough)
9
grim(adjective, tough, firm, resist, determined)
9
stern(adjective, characteristic, obstinate, insistent)
8
determined(adjective, strong, hard, tough, firm)
8
strong(adjective, hard, tough, firm, determined)
7
indomitable(adjective, characteristic, strong, hard, tough)
7
uncompliant(adjective, tough, resist, unreasonable, grim)
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APASmart Define. (2015). iron thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/iron/thesaurus/synonyms
ChicagoSmart Define. 2015. "iron thesaurus" https://smartdefine.org/iron/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2015, iron thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/iron/thesaurus/synonyms>.
MLASmart Define. "iron thesaurus" 14 April 2015. Web. 20 September 2026. <https://smartdefine.org/iron/thesaurus/synonyms>